As a method of observing a tubular structure on the basis of volume data (medical 3D image data) obtained by an X-ray CT (Computed Tomography) device, a magnetic resonance imaging device (hereinafter referred to as an MRI device) and the like, an MPR (Multi-Planner Reconstruction) method, a curved multi-planner reconstruction (CPR) method, and a stretched CPR method (hereinafter referred to as an SPR method) are known.
The MPR method is a method in which 3D data is cut off on a plane in an arbitrary direction and a sectional image seen from a direction perpendicular to this plane is reconstructed. On the other hand, the CPR method is a method mainly used when a tubular structure in the 3D image data is to be observed, in which the 3D image data is cut off along a core line of the tubular structure and the sectional image along the core line of the tubular structure is reconstructed by projecting this curved plane to a predetermined projection plane. The SPR method is a method of further stretching the core line extracted by the CPR method linearly. According to these methods, a user can easily observe the section of the tubular structure.
However, these sectional images are only images of one section of a tubular structure. The sectional image obtained by the CPR method, for example (hereinafter referred to as a CPR image) has only information which can be caught on a specific section along the core line of the tubular structure, and images of a portion of interest such as stricture or hypertrophy present at a position dislocated in a depth direction with respect to this section cannot be included. Therefore, when the user observes the CPR image, it is extremely difficult to discover the portion of interest not included in the CPR image.